Principal Investigator: Giacomo Rizzolatti
Mechanisms and Circuits for Space and Object Attention
There is growing consensus that selective attention is mediated by multiple cortical circuits. As far as spatial attention is concerned, there is agreement that one of the circuits mostly involved in it consists of the posterior parietal cortex and the frontal eye field region. It is debated, however, if the circuits mediating spatial attention are specialized attentional circuits or, on the contrary, attention derives from an activation of circuits the primarily role of which is the processing of sensory-motor information. For attention to objects there is evidence that circuit including inferotemporal cortex should mediate this function. However, some recent data suggest that also the areas of the dorsal stream could intervene in object selection.
The aim of the present project is: a) to assess wether the perceptual salience of a visual stimulus is enhanced by the preparation of an action directed toward an object the intrinsic characteristics of which (e.g. size, shape, orientation) are congruent with those characterizing the visual stimulus. b) To trace the circuit responsible for spatial attention and possibly to establish the temporal sequence in which the various cortical areas forming this circuit are activated. c) To trace the circuit that becomes active when a subject prepares an object-directed action and to establish wether the motor activation may justify an increase of perceptual salience of congruent object by spreading towards the parietal and occipital cortex. d) To test directly the hypothesis that a premotor activation is responsible for an increase of stimulus salience in spatial and object directed tasks by temporarily inactivating the premotor cortices in humans. e) To provide a neurophysiologically-motivated model of the attentional mechanisms, that is based on premotor activation and on a consequent recurrent activation of posterior "perceptual" areas.
In order to achieve the goals of the project, the following methodological
paradigms will be used: 1) reaction time (RT) experiments, ii) recordings
of event related potentials using combined EEG-MEG technique, iii) combined
RT and transcranial magnetic stimulation JMS) experiments, iv) simulation
of biological plausible model. Experiment with RTs and TMS will be carried
out in Parma, whereas those involving EEG-MEG technique will be performed
in Helsinki, thanks to an agreement with Low Temp. Lab., Espoo, Helsinki
University, Finland. Computational modelling will be carried out by the
team of Prof. C. Umilta in Padua, Italy. This part of the project is outside
of our competence and represents the contribution of the Padua team with
which the present project is bundled.
